Question

Mean of 9 observations was found to be 35. Later on, it was detected that an observation 81 was misread as 18, then the correct mean of the observations is ______.

• A. 40
• B. 41
• C. 42
• D. 43

Answer 1

The correct option is C 42

Incorrect mean of 9 observations $=35$
Incorrect sum of observations $=35\times 9=315$
Since, 81 is misread as 18.
So, correct sum of observations
$=315-18+81=378$
$\therefore$ Correct mean $=\frac{378}{9}=42$